This study will examine whether the drug ranibizumab (Lucentis) can help prevent vision loss in people with macular telangiectasia, a condition in which new blood vessels grow in the retina at the back of the eye and can leak. Such changes in blood vessels are seen in other diseases associated with changes in a body chemical called vascular endothelial growth factor (VEGF). Ranibizumab is an anti-VEGF drug that is effective in treating another eye disease, age-related macular degeneration, with similar changes in eye blood vessels. People 18 years of age and older with macular telangiectasia in both eyes and new blood vessel growth in at least one eye may be eligible for this study. They must have vision better than 20/400 in the study eye.